MissionPlanner disarms after a few seconds

In the Machine planner, I cannot use the arm while using a quadcopter. If I do force arm then it’s disarmed automatically.

It is normal that it disarms after a few seconds if you do not takeoff.

If it doesn’t arm normally them you have an issue that you must fix instead of force arming.

You should find out what exactly is the issue instead of force arming it. And do NOT disable arming checks. They are there for a reason.